A die attach material for bonding, for example, a silicon carbide (SiC) chip to a substrate, and a sealing material and a conductive paste for electronic parts, such as a ceramic package containing therein an integrated circuit device, and a display device, are desired to achieve bonding at relatively low temperatures, taking into consideration the properties of objects to be bonded or to be sealed which are extremely sensitive to heat. As a conductive paste which can achieve bonding at low temperatures, a composition comprising glass having a low melting point is used.
Conventionally, as low melting-point glass, PbO—B2O3 glass having a low melting point has been known. Patent document 1 discloses, as glass having a low softening point, glass comprising 20 to 70% of silver oxide, 10 to 70% of an oxide of vanadium or molybdenum, and 10 to 70% of an oxide of a semi-metal selected from the group consisting of phosphorus, germanium, arsenic, antimony, bismuth, and tellurium (patent document 1).
With respect to glass which can be calcined at a temperature lower than the calcination temperature for the conventional low melting-point PbO—B2O3 glass, patent document 2 discloses low melting-point glass comprising Ag2O: 8 to 20%, MoO3: 20 to 35%, ZnO: 1 to 6%, TeO2: 30 to 55%, and V2O5: 5 to 19% (patent document 2).
With respect to glass used in, for example, a die attach material, there is disclosed glass comprising, for example, Ag2O in an amount of about 40 to 65% by mass, V2O5 in an amount of about 15 to 35% by mass, and at least one oxide selected from the group consisting of TeO2, PbO2, and Pb3O4 in an amount of about 0 to 50% by mass, in terms of the oxide, wherein the glass forms a Ag2O—V2O5—TeO2—PbO2 crystal (for example, patent document 3). The glass disclosed in patent document 3 is used in, for example, a ceramic package containing therein a temperature-sensitive integrated circuit device as a paste for bonding the temperature sensitive device at a low temperature (for example, at 350° C.).
The cited document 4 discloses a glass composition which comprises Tl2O3 in an amount of 60 to 82.5% by weight, V2O5 in an amount of about 2.5 to 27.5% by weight, and P2O5 in an amount of about 2.5 to 17.5% by weight, in terms of the oxide, and which has a boundary temperature of about 350° C. or lower at which vitrification occurs (patent document 4). Patent document 4 discloses that the glass composition has a boundary temperature of 460° C. or lower at which no devitrification occurs. The devitrification means that molten glass suffers crystal deposition of part of the glass having a certain composition during, for example, solidification of the molten glass upon cooling.
Patent document 5 discloses a paste comprising conductive metal particles, a glass composition, an organic solvent, and a resin. Patent document 5 has a description showing that the glass composition specifically preferably has a remelting temperature of 275° C. or lower. Patent document 5 has a description showing that when the glass composition contained in the paste has a high remelting temperature, the amount of the glass phase which satisfactorily wets the surface of an adherend is reduced, so that the bond strength of the paste becomes poor. The cited document 5 discloses that the combination of TeO2 and PbO2 in the respective optimal amounts provides glass having crystalline properties and low-temperature properties desirable in respect of the structure finally obtained.